Process for the manufacture of lead beta-resorcylates

ABSTRACT

DIBASIC AND MONOBASIC LEAD BETA RESORCYLATES ARE PRODUCED BY THE REACTION OF LEAD MONOXIDE AND BETA-RESORCYCLIC ACID IN AN ORGANIC SOLVENT MEDIUM IS SELECTED MOLAR RATIOS.

3,748,349 PROCESS FDR THE MANUFACTURE OF LEAD BETA-RESORCYLATES Daniel R. Satriana, Verona, N.J., assignor to the United States of America as represented by the Secretary of the Army No Drawing. Filed July 28, 1971, Ser. No. 166,973 Int. Cl. C07f 7/24 US. Cl. 260-435 13 Claims ABSTRACT OF THE DISCLOSURE Dibasic and monobasic lead beta resorcylates are produced by the reaction of lead monoxide and beta-resorcylic acid in an organic solvent medium in selected molar ratios.

This invention described herein may be manufactured, used and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

Ballistic modifiers are used in rocket propellant formulations to control the burning rate of the propellant over a given pressure region. Two of the most effective ballistic modifiers have been monobasic and dibasic lead betaresorcylate. Unfortunately, the aforesaid propellant composition incorporating these modifiers, on standing for several months at ordinary temperatures, developed a white crystalline growth on the surface thereof, which acted as an ignition inhibitor. This in turn produced ignition failures, which represent a serious problem with such propellant compositions. The crystalline exudate has been found to consist essentially of beta-resorcylate acid which appears to be an effective ignition inhibitor and is apparently produced because of impurities in the chosen lead salt. Use of reduced concentrations of the modifier was tried to eliminate this blooming effect but such change only led to improper ballistic activity.

Analysis of the monobasic or dibasic lead beta-resorcylate modifiers employed showed that it was, in fact, an impure mixture of monobasic, dibasic and other lead beta-resorcylate salts. This suggested that one form of the salt could be responsible for the exudate. Clearly a a method had to be devised to produce essentially pure monobasic and dibasic lead beta-resorcylate so that original concentrations of the modifier could be maintained and blooming prevented.

It is therefore an object of this invention to provide processes for the manufacture of analytically pure monobasic and dibasic lead beta-resorcylate s.

Yet another object of the invention is to provide pure monobasic or dibasic lead beta-resorcylate which may be used as ballistic modifiers in propellant compositions.

A further object is to provide a ballistic modifier which will eliminate the problem of beta-resorcylic acid formation on propellant surfaces.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same become better understood from the following detailed description.

According to the process of my invention, dibasic lead beta-resorcylate having the following probable chemical structure,

OH H

in; in

can be obtained in high purity and excellent yield by re- United States Patent 0 acting lead monoxide and beta-resorcylic acid in molar ratio of about 1:3 or greater in a water miscible organic solvent, preferably ethyl alcohol.

Similarly, monobasic lead beta-resorcylate having the following probable chemical structure,

can be obtained in high purity and yield by reacting lead monoxide and beta-resorcylic acid in about a 1:2 molar ratio in an anhydrous organic solvent, preferably ethyl alcohol.

The process may be carried out in any solvent miscible with water and in which resorcylic acid is soluble. Examples include methanol, acetone, ethanol, dimethyl formamide and tetrahydrofurane. Further, the process may be carried out in mixtures of water and the above solvents or mixtures of the above solvents themselves.

The monobasic or dibasic lead beta-resorcylate product is separated from the solvent medium by the steps of filtering, washing the precipitate with a solution identical to the solvent medium and drying the precipitate.

Although it is not intended that the invention be limited thereto, there is set forth herein below for purposes of illustration, examples of how the monobasic and dibasic lead beta-resorcylate may be produced.

EXAMPLE I Preparation of monobasic lead beta-resorcylate 11.16 g. (0.05 mole) of lead monoxide (PbO) is added to ml. of absolute ethyl alcohol containing 16.96 g. (0.11 mole) of practical grade beta-resorcylic acid. The mixture is heated at 60-70 C. for 1.5 hours with constant stirring. The product is filtered while still warm, washed twice with a small amount of warm (60 C.) absolute alcohol, and dried in the oven at 60 C. for several hours. The dry product thus obtained weighed 16.1 grams and was essentially pure monobasic lead beta-resorcylate as shown by the following elemental analysis Percent by weight Found: Pb57.29, C23.70, H1.l8 Calculated: Pb57.66, C23 .75, Hl.12

The product weighed 16.1 grams (theory 18.0 grams) which corresponds to a yield of 89.5% of theory based on the amount of PbO consumed in the reaction.

EXAMPLE -II Preparation of bibasic lead beta-resorcylate 11.16 g. (0.05 mole) of lead monoxide (PbO) is added to ml. of 50% (by volume) of ethyl alcohol containing 23.1 g. (0.15 mole) of practical grade beta-resorcylic acid. The mixture is stirred at ambient temperature under a current of air for five hours. The solid is filtered, washed with ice cold 50% ethyl alcohol, and dried in the oven at 100 C. to constant weight. The dry product thus obtained weighed 23.8 grams and was essentially pure dibasic lead beta-resorcylate as shown by the following elemental analysis.

Percent by weight Found: Pb40.53, C-32.85, H2.l0 Calculated: Pb40.35, C32.75, H1.96

The product weighed 23.8 grams (theory 25.7 grams) which corresponds to a yield of 92.5% of theory based on the amount of PbO consumed in the reaction.

Elemental analysis (lead, carbon and hydrogen) of the above two products is within experimental error of the theoretical values calculated for the chemical structures of monobasic and dibasic lead beta-resorcylate.

Analysis of the carbon and hydrogen content was accomplished by combustion product measurement while lead content was found by electrolytic methods.

Further results of variations in the process are shown in the following table.

beta-resorcylic acid per mole of lead monoxide in an inert, water miscible organic solvent medium in which beta-resorcylic acid is soluble.

2. A process for producing dibasic lead betaresorcylate comprising contacting lead monoxide with betaresorcylic acid in a molar ratio of at least about 1:3 in an inert water miscible organic solvent medium in which beta-resorcylic acid is soluble.

3. The process of claim 2 wherein the reaction tem- TABLE lip-DEVELOPMENT OF OPTIMUM C(bDITIONS FOR THE SYNTHESIS OF LEAD BETA-RESOR- LATE SALTS Reaction temper- Reaction Analysis (p rc ature time Yield Mole ratio (PbO/B RA) (hours) Solvent medium (percent) Pb C H Product 60-70 1. Ethanol (ABS).-- 89. 5 57. 29 23. 70 1. 18 Pure monobasie salt. 60-70 1. 5 do 5.0 38- 58- 31. 96 2. 46 Dibasic salt (2nd traction). 60-70 1. 5 Ethanol (50%) 50. 3 57. 69 23. 66 1. 21 Pure monosbsic salt. 60-70 1. 5 do 19. 5 38. 21 31. 89 2. 56 Dibasic salt (2nd fraction).

( 4. 5 78. 7 39. 81 31. 70 2. 16 Dibasic salt. 5. 0 76. 0 41. 01 31. 90 2. 08 0. 0) 5. 0 Ethanol (50%) 92. 5 40. 53 32. 35 2. 10 Pure dibasic salt. 40. 35 32. 75 1. 96 Calculated. 57. 66 23. 40 1. 12 Do.

1 Room temperature. 1 Dibasic lead beta-resorcylate.

a Monobasic lead beta-resorcylate.

It can readily be seen from the above table that optimum yield for the monobasic salt occurs when absolute ethanol is the solvent medium, the molar ratio of lead monoxide to beta-resorcylic acid is about 1:2, and the reaction temperature is 60-70 C. As the ratio approaches a 1:1 ratio an incomplete reaction occurs yielding the monobasie salt in less than preferred percent yield. As the ratio approaches a 1:3 ratio more dibasic salt formation occurs.

Optimum yield of the dibasic salt occurs when the reaction is carried out in a 50% aqueous ethanol solution at ambient temperatures with a molar ratio of about 1:3. Higher molar ratios (1:4, 1:5, etc.), although yielding the dibasic salt in high concentration, have the disadvantage of insoluble unconsumed beta-resorcylic acid remaining in solution which requires the time consuming extra step of removal by solvent extraction.

Further the reaction may be carried out at a temperature above the optimum range of ambient to 70 C., however decomposition and hydrolysis of the beta-resorcylic acid into resorcinol will occur appreciably at temperatures over 100 C.

Second fraction recovery in Table I is accomplished by reduction in volume of the solvent medium filtrate thereby crystallizing out the more soluble dibasic salt.

Thusly, through the practice of my invention, processes for the production of essentially pure monobasic and dibasic lead beta-resorcylates are achieved. The availability of essentially pure dibasic and monobasic lead beta-resorcylate by means of my invention allows the use of the salts as ballistic modifiers without the danger of resorcylic acid blooming upon prolonged storage. Secondly, analytic standards may now be acquired (X-ray diifraction, infrared spectroscopy, thermogravimetric analysis, diiferential thermal analysis, etc.) so that specification standards can be developed for commercial procurement of the essentially pure monoand dibasic lead beta-resorcylate.

I wish it to be understood that I do not desire to be limited to the exact details and compositions described in this specification for obvious modification will occur to a person skilled in the art.

I claim:

1. A process for producing a basic lead beta-resorcylate comprising contacting lead monoxide with betaresorcylic acid in a ratio of at least about 2 moles of perature is between ambient temperature and 70 C.

4. The process of claim 2 wherein the dibasic lead betaresorcylate is recovered by separation, washing the separated solid with a solvent identical to the solvent medium, and drying the resultant solid.

5. The process of claim 2 wherein the solvent is selected from the group consisting of ethanol, methanol, acetone, dimethyl formamide, tetrahydrofuran and mixture thereof.

6. The solvent of claim 5 wherein the solvent is combined with water to form the solvent medium.

7. The solvent of claim 5 wherein the solvent medium is 5 0% aqueous ethyl alcohol.

8. A process for producing monobasic lead beta-resorcylate comprising contacting lead monoxide with betaresorcylic acid in a molar ratio of about 1:2 in an inert water miscible organic solvent medium in which betaresorcylic acid is soluble.

9. The process of claim 8 wherein the reaction temperature is between ambient temperature and 70 C.

10. The process of claim 8 wherein the monobasic lead beta-resorcylate is recovered by separating, washing the separated solid with a solvent identical to the solvent medium, and drying the resultant solid.

11. The process of claim 8 wherein the solvent is chosen from the group consisting of ethanol, methanol, acetone, dimethyl formamide, tetrahydrofuran and mixtures thereof.

12. The solvent of claim 11 wherein the solvent is combined with water to form the solvent medium.

13. The solvent of claim 11 wherein the solvent medium is absolute ethanol.

References Cited UNITED STATES PATENTS 2,391,166 12/1945 Kebrich 260435 R 2,421,706 6/ 1947 Kebrich 260435 R FOREIGN PATENTS 595,127 11/1947 Great Britain 260435 R OTHER REFERENCES Chemical Abstracts, vol. 57, 2486 eg (1962). Chemical Abstracts, vol. 59, 6191 e.

HELEN M. S. SNEED, Primary Examiner 

